In the ALD method that is of one of thin-film forming techniques, two kinds of gases composed mostly of elements constituting a film to be formed are alternately supplied onto a deposition target substrate, and the thin film is repeatedly formed plural times in units of atomic layers on the substrate, thereby forming the film having a desired thickness. For example, a source gas containing Si and an oxidation gas containing O are used when a SiO2 film is formed on the substrate. A nitridation gas is used instead of the oxidation gas when a nitride film is formed on the substrate.
So-called growth self-stopping action (self-limiting function) is utilized in the ALD method. That is, only a source gas component for one or several layers is adsorbed to a substrate surface while the source gas is supplied, but the excess source gas does not contribute to the growth.
When compared with a general CVD (Chemical Vapor Deposition) method, advantageously the ALD method has both high step coverage and film-thickness controllability. Therefore, the ALD method is expected to be practically applied to the formation of a capacitor for a memory element or an insulating film called “high-k gate.” Additionally, because the insulating film can be formed at a temperature of 300° C. or less in the ALD method, the ALD method is also expected to be applied to the formation of a gate insulating film for a thin-film transistor in a display device such as a liquid crystal display in which a glass substrate is used.
For example, Patent Document 1 describes an ALD apparatus for forming the thin film on the substrate, including a source gas adsorption chamber in which at least one kind of the source gas is adsorbed to the substrate, a reactive gas irradiation chamber in which the substrate is irradiated with at least one kind of a reactive gas, and means for changing the substrate between the source gas adsorption chamber and the reactive gas irradiation chamber.
The apparatus of Patent Document 1 is implemented to provide the apparatus that can efficiently perform the deposition without requiring frequent maintenance of the deposition chamber in vacuum deposition by the ALD method.